What is Email Syntax Error?

Have you ever thought about what characters are allowed in an email address or what are the rules for an email address syntax? In the world of computer and programming languages, it is well known that and extra white space or dot could break a program or action. In the world of emails, there are exactly the same rules. A correct email address needs to have some standard parts. If every part does not follow its rules, a syntax error will show up. To make it more clearly, I want to provide a valid email address: [email protected]. This address has no syntax error. If I add an extra dot, then it becomes a syntax error: [email protected].

Each email address has three main parts. Here they are:

1. Recipient Name or Local Part
2. @ Symbol
3. Domain Part

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Main parts of an email address.

I am going to describe each part of and standard email address.

Local Part

The local part or the recipient name is what exactly comes before the @ symbol. It could be name of the account holder, a role in a company like manager, or a department. There are specific and define characters that can be used in local part:

1. Lowercase and uppercase Latin letters A-Z and a-z
2. Digits from 0 to 9
3. Dot ., provided that it is not the first or last character unless quoted, and provided also that it does not appear consecutively unless quoted. For example, [email protected] is not allowed but "mark..russell"@example.com is allowed
4. Space and "(),:;<>@[\] characters are allowed with restrictions. They are only allowed inside a quoted string, and in addition, a backslash or double-quote must be preceded by a backslash
5. Comments are allowed with parentheses at either end of the local-part. For example mark.russell(comment)@server.com and (comment)[email protected] are both equivalent to [email protected].

Despite all above mentioned characters are logically valid, some email providers may restricted the use of some characters. Moreover, email addresses could be sensitive against upper and lowercase. However, most of email servers are configured to consider all the cases as the same inbox. It is worth mentioning that the local part cannot exceed 64 characters.

@ Symbol

I think this is easy to guess. There must be only one @ after the local part which separates the local-part and the domain-part.

Domain Part

A domain name consists of one or more sections, technically referred to as labels, typically interconnected and separated by dots. For instance example.com.

Domain Name (Second-Level Domain)

A domain name is a series of letters and digits describing a space owned and operated by a single mailbox provider or entity on the Internet. These characters are allowed for the domain name part:

1. Lowercase and uppercase Latin letters A-Z and a-z
2. Digits from 0 to 9
3. Hyphen: -
4. IP address surrounded by square brackets: mark.russell@[192.168.2.1] or mark.russell@[IPv6:2001:db8::1]
5. Dot ., In case a subdomain is used. Example: [email protected]

TLD or Top-Level Domain

The top-level domain is expressed by the right-most label; for example, the domain name www.debounce.io is part of the top-level domain io.

Here are the five most common domain extensions to consider in 2020.

• .com
• .net
• .org
• .co
• .us

It is worth mentioning that the domain part (domain name + TLD) cannot exceed 255 characters.

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Domain part explained.

Examples

Here are some examples of valid and invalid email syntaxes for better understanding.

Can You Include or Use a Dash in an Email Address?

When creating an email address, one question often arises: whether you can include a dash (-) character within the username portion. The short answer is yes - dashes are a valid character that can be used in an email username. However, there are some important things to know about using dashes in email addresses.

The email specification, known as RFC 5322, does not explicitly forbid using dashes. As long as the character falls within the allowed set for user names, it should be compatible across email systems. Other permitted characters include letters, numbers, periods, and some symbols. So, dashes satisfy the technical rules for valid inclusion.

Most major email providers like Gmail, Outlook, Yahoo, and others support dashes without issue. They will not cause any problems when receiving, sending or logging into an email account. Dashes are treated just like any other allowed special character.

However, there is one potential downside to including dashes. Dashes may be stripped out or misinterpreted in some older or less sophisticated email systems. This can cause message delivery, logins, or address recognition/parsing issues. While modern servers handle dashes well, there is a risk of sporadic compatibility problems with antique systems that are still around.

Human users may also find dashes confusing when manually transcribing or remembering an email address. It's an extra symbol to parse compared to an all-lowercase name without punctuation. Typing errors become more likely. Spam filters also sometimes treat dashes as red flags, so an address with dashes could attract more junk than one without.

In general, dashes work fine, but it's safest to avoid them unless you have a specific reason to use one, like bridging a double last name. Sticking to basic characters helps maximize compatibility and minimize human entry mistakes. But if you have an address with dashes, don't worry - it will function normally on any contemporary email provider.

In conclusion, dashes are technically valid characters for email addresses and are supported by major email services. However, there is a slight risk of compatibility issues with very old systems. And humans may find dashes harder to interpret accurately. Unless you have a compelling reason, creating email usernames without punctuation is usually best for maximum simplicity and cross-system reliability. But rest assured, dashes can be safely used if desired.